It is well-known that curing is a key procedure in tire manufacturing process. In this procedure, the present curing method is that the curing bladder and the outer mold are used together to support pressure and heat for the green tire. Cross-linking reaction takes place between compound and vulcanizing agent at this condition, which eventually gives tire good performance and pattern. Compared with the early water bag shaping method, bladder shaping method is widely used in the manufacture of tires due to its high heat transfer efficiency, but this method has some faults still, such as:
Firstly, curing bladder shows often an incomplete or asymmetric structure owing to viscose and unreasonable design, which results in uneven mass distribution of the cured tire, On the other hand, the mass distribution of the green tire is also uneven by the influence of building precision. But, the flexible bladder which provides low pressure cannot make compound distributes evenly again during curing. As a result, the balance and uniformity of the completed product is low.
Secondly, the curing process needs to consume large amounts of steam or superheated water, but a small part of these thermal medium is absorbed by tire, and most of them is consumed in invalid pipeline loops which causes serious energy waste.
Thirdly, as is known, temperature and pressure of steam is associated with each other. They cannot be controlled individually. So, curing temperature is often low when curing pressure is suitable. This problem is solved by prolonging curing time generally. But, it reduces productivity.
Fourthly, the shoulder and bead of tires are more difficult to cure than other parts. Therefore, they need more heat to reach the plateau of vulcanizing curves. However, in the actual curing process, steam in the bladder transfers heat to the whole green tire uniformly, and each part acquires the same heat energy. Therefore, the crown and sidewall of tires have been over cured severely when the shoulder and bead reach the plateau of vulcanizing curves, which greatly degrade performance of the tire.
In recent years, nitrogen curing technology is developed based on the principle of constant pressure and variable temperature. Although this technology obviously saves energy and improves the curing efficiency, it brings a problem, which is that steam will be condensed and deposited in the bottom of bladder when nitrogen is injected into bladder. And, it cause the temperature difference between upper and low sidewalls. So curing quality of tire is low.
The references numbers refer to the following:                1. the small segment of inner mold        2. the upper connecting rod of telescoping mechanism of small segment        3. the inner axle sleeve        4. the outer axle sleeve        5. clamping ring        6. bolt        7. axle-end ring        8. positioning pin        9. the upper connecting rod of telescoping mechanism of large segment        10. the large segment of inner mold        11. melt pressure sensor        12. supporting plate for large segment        13. the low connecting rod of telescoping mechanism of large segment        14. the short connecting rod of telescoping mechanism of large segment        15. copper sleeve        16. base        17. piston        18. the short connecting rod of telescoping mechanism of small segment        19. the low connecting rod of telescoping mechanism of small segment        20. supporting plate for small segment        21. thermocouple        22. phase change material        23. “|” shaped core        24. silica gel        25. insulation layer a        26. electromagnetic induction coil a        27. shell        28. “∪” shaped core        29. electromagnetic induction coil b        30. insulation layer b        31. outer mold        32. cover        33. green tire        34. steel ring below        